Knowing the composition, nature and amount of crust at the surface of the early Earth is crucial to understanding the early geodynamics of our planet. Yet our knowledge of the Hadean-Archean crust is ...far from complete, limited by the poor preservation of Archean terranes, and the fact that less attention has been paid to the sedimentary record that tracks erosion of these ancient remnants. To address this problem and get a more comprehensive view of what an Archean continent may have looked like, we investigated the trace element and Sm-Nd, Lu-Hf isotopic records of Archean metasedimentary rocks from South Africa. We focused our study on sandstone and mudstone from drill core in the Fig Tree Group (3.23–3.26Ga) of the Barberton granite-greenstone belt, but also analyzed the 3.4Ga Buck Reef cherts and still older (3.5–3.6Ga) meta-igneous rocks from the Ancient Gneiss Complex, Swaziland.
Based on principal component analysis of major and trace element data, the Fig Tree metasedimentary rocks can be classified into three groups: crustal detritus-rich sediments, Si-rich sediments and Ca-, Fe-rich sediments. The detritus-rich sediments have preserved the Sm-Nd and Lu-Hf isotopic signatures of their continental sources, and hence can be used to constrain the composition of crust eroded in the Barberton area in the Paleoarchean period. Based on Sm/Nd ratios, we estimate that this crust was more mafic than today, with an average SiO2 content of 60.5±2wt.%. This composition is further supported by isotopic mixing calculations suggesting that the sedimentary source area contained equal proportions of mafic-ultramafic and felsic rocks. This implies that the Archean crust exposed to weathering was more mafic than today but does not exclude a more felsic composition at depth. Neodymium and Hf crustal residence ages show that the eroded crust was, on average, ∼300–400Ma older than the deposition age of the sediments, which highlights the importance of intracrustal reworking of older crust at ∼3.2Ga in the Barberton area.
The Si-rich sediments have slightly positive εNd (t=3.23Ga) but extremely radiogenic εHf (t=3.23Ga), up to +11. Based on analyses of 3.4Ga Buck Reef cherts, we suggest that the radiogenic Hf isotopic signature of the Si-rich sediments can be accounted for by the old chert clasts or detrital silicified rock fragments present in the rocks. The latter have extremely high Lu/Hf ratios such that their εHf values would increase dramatically, by about +100 epsilon units every 100Ma. In the Ca-, Fe-rich sediments, one sample contains carbonate that preserves the typical rare-earth element features of seawater precipitates. The initial Nd isotopic composition of this sample (εNd (t=3.23Ga)= +1.7) is within the range of previous estimates for Archean anoxic seawater.
The 146Sm–142Nd extinct decay scheme (146Sm half-life of 103 My) is a powerful tool to trace early Earth silicate differentiation. Differences in 142Nd abundance measured between different chondrite ...meteorite groups and the modern Earth challenges the interpretation of the 142Nd isotopic variations found in terrestrial samples because the origin of the Earth and the nature of its building blocks is still an ongoing debate. As bulk meteorites, the enstatite chondrites (EC) have isotope signatures that are the closest to the Earth value with an average small deficit of ∼10 ppm in 142Nd relative to modern terrestrial samples. Here we review all the Nd isotope data measured on EC so far, and present the first measurements on an observed meteorite fall Almahata Sitta containing pristine fragments of an unmetamorphosed enstatite chondrite belonging to the EL3 subgroup. Once 142Nd/144Nd ratios are normalized to a common chondritic evolution, samples from the EC group (both EL and EH) have a deficit in 142Nd but the dispersion is important (μ142Nd=−10±12 (2SD) ppm). This scatter reflects their unique mineralogy associated to their formation in reduced conditions (low fO2 or high C/O). Rare-earth elements are mainly carried by the sulfide phase oldhamite (CaS) that is more easily altered than silicates by weathering since most of the EC meteorites are desert finds. The EL6 have fractionated rare-earth element patterns with depletion in the most incompatible elements. Deviations in Nd mass independent stable isotope ratios in enstatite chondrites relative to terrestrial standard are not resolved with the level of analytical precision achieved by modern mass spectrometry techniques. Here we show that enstatite chondrites from the EL3 and EL6 subgroups may come from different parent bodies. Samples from the EL3 subgroup have Nd (μ142Nd=−0.8±7.0, 2SD) and Ru isotope ratios undistinguishable from that of the Bulk Silicate Earth. EL3 samples have never been analyzed for Mo isotopes. Because these enstatite chondrites are relatively small in size and number, they are usually not available for destructive isotopic measurements. Average values based on the measurement of EL6 samples should not be considered as representative of the whole EL group because of melting and thermal metamorphism events affecting the Sm/Nd ratios and prolonged open-system history. The EL3 chondrites are the best candidates as the Earth's building blocks. These new results remove the need to change the composition of refractory incompatible elements early in Earth's history.
•Here we present the first high precision Nd isotope measurements on an EL3 observed meteorite fall.•MS-177 is a pristine and unmetamorphosed fragment coming from the polymict breccia Almahata Sitta.•Enstatite chondrites from the EL3 and EL6 subgroups may come from different parent bodies.•The EL3 chondrites are the best candidates as the Earth's building blocks.•These results remove of refractory incompatible elements early in Earth's history.
The purpose of this study was to evaluate the dose-dependent effect of human milk fortifier (HMF) on the osmolality of various preterm human milks (PHMs) at different gestational and lactation ...stages, and with different storage and treatment conditions that are routinely used in neonatal intensive care units (NICUs).
Twenty-four mothers who had given birth to their baby before 28 or between 29 and 31 weeks of pregnancy participated in the study after 1–2 weeks or 3–4 weeks breastfeeding after delivery. The study was a prospective, multicenter, comparative, and noninterventional study. Osmolality of fresh or pasteurized human milk stored at 4°C was measured (cryoscopy) at baseline, and 24hours after adding Suppletine® Human Milk fortifier (SHMF) at 3%, 4%, 4.5%, and 5% (w/v).
PHM without supplementation had an osmolality (mean±SD) of 301±8 mOsm/kgH2O (n=40; 95% CI: 298; 303). Adding 3–5% SHMF induced a linear increase of osmolality (P<0.001; r2=0.975). With 4% SHMF, the osmolality measure was 443±13mOsm/kg H2O (95% CI: 439–447). Neither a 24-hour storage at 4°C nor pasteurization induced a modification of osmolality compared to the fresh samples.
Whatever the origin and quality of milk as well as hospital practices, adding up to 4% (w/v) SHMF to PHM increases its nutritional quality and osmolality without exceeding 450mOsm/kgH2O, which is generally recognized as safe.
Komatiites and sedimentary rocks sampled during the International Continental Drilling Program (BARB1-2–3-4–5) in the Barberton greenstone belt, South Africa, were analyzed for 146Sm-142Nd ...systematics. Resolved negative μ142Nd values (down to −7.7 ± 2.8) were identified in komatiites from the 3.48 Ga Komati Formation and this signature correlates with low Hf/Sm ratios measured in these samples. The negative μ142Nd point to a source with subchondritic Sm/Nd ratio which formed during the Hadean. No analytically resolvable 142Nd anomalies were measured in crustal detritus-rich, Si-rich, Ca-Fe-rich sediments and cherts from the Buck Reef (3.42 Ga) and the Fig Tree Group (3.23–3.28 Ga). Our new measurements are incorporated into a larger set of 147Sm-143Nd and 176Lu-176Hf data to better understand the 142,143Nd-176Hf isotope signatures in the mantle source at the time of komatiite crystallization. Our calculations show that the 142,143Nd-176Hf isotope signatures and Hf/Sm ratios cannot be produced by recycling into the komatiite source of detrital sediments like those sampled in the Barberton area. Only cherts have the required trace element characteristics – low Hf/Sm, radiogenic ε176Hf –but the trace element concentrations in the cherts are so low that unrealistic amounts of chert would need to be added.
We propose a four-stage model for the formation of these rocks. Negative μ142Nd and low Hf/Sm ratios developed during the crystallization of a deep magma ocean soon after Earth accretion. The material that ultimately became the source of komatiites was a residual liquid produced by 50% crystallization leaving a bridgmanite/ferropericlase/Ca-perovskite cumulate. The Lu-Hf and Sm-Nd isotope systems were decoupled at this stage. After extinction of 146Sm around 4 Ga, parent/daughter ratios fractionated during a melt extraction event. With this model we explain the positive ε176Hf and slightly negative ε143Nd in these samples. The 3.55 Ga Schapenburg komatiites in another part of the Barberton belt share similar chemical signatures, supporting our model of fractionation in a deep magma ocean early in Earth's history.
The short-lived Sm146→142Nd isotope system (t1/2=103 Ma) provides constraints on the timing and processes of terrestrial silicate fractionation during the early Hadean. Although some Archean terranes ...preserve variability in 142Nd/144Nd, no anomalies have been resolved previously in young rocks. This study provides high precision 142Nd/144Nd data on a suite of ocean island basalts from Samoa and Hawaii previously shown to have variable depletions in 182W/184W that are inversely correlated with 3He/4He ratios. Improved analytical techniques and multiple replicate analyses of Nd show a variation in μ142Nd values between −1.3 and +2.7 in the suite, relative to the JNdi standard. Given the reproducibility of the standard (±2.9 ppm, 2 SD), two Samoan samples exhibit resolved variability in their 142Nd/144Nd ratios outside of their 95% confidence intervals, suggesting minor variability in the Samoan hotspot. One sample from Samoa has a higher μ142Nd of +2.7, outside the 95% confidence interval (±1.0 ppm) of the average of the JNdi standard. Limited, but resolved, variation in 142Nd/144Nd within the suite suggests the preservation of early Hadean silicate differentiation in the sources of at least some basalts from Samoa. Larger variations of 182W/184W and 3He/4He ratios in the same samples suggest that metal–silicate separation and mantle outgassing left a more persistent imprint on the accessible mantle compared to 142Nd/144Nd ratios which are impacted by early silicate differentiation.
•OIB with large correlated 182W–3He range show little variation in 142Nd/144Nd.•Small, but resolved 142Nd difference among Samoa hotspot basalts.•Limited preservation of earliest silicate differentiation in modern accessible mantle.
The CLAS12 Geant4 simulation Ungaro, M.; Angelini, G.; Battaglieri, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2020, Volume:
959, Issue:
C
Journal Article
Peer reviewed
Open access
The Geant4 Monte-Carlo (GEMC) package is used to simulate the passage of particles through the various CLAS12 detectors. The geometry is implemented through a database of Geant4 volumes created ...either through the GEMC native API, by the CLAS12 geometry service, or imported from the CAD engineering model. The truth information is digitized with a plugin mechanism by routines specific to each detector and includes the use of the CLAS12 calibration database constants to produce both ADC and TDC response functions. Theoretical models that produce the generated events interface with GEMC through the LUND data format. The merging of simulated data with real random trigger data provides a mechanism to include both beam and electronic background into the simulation of generated events to accurately model beam data from the CLAS12 detector. The performance of simulation is demonstrated by comparison with the experimental data.
Le syndrome de Hurler, forme la plus sévère de mucopolysaccharidose de type I, est une maladie rare de surcharge lysosomale : l’accumulation de glycosaminoglycanes (GAG) est à l’origine du ...dysfonctionnement progressif de multiples organes. Nous rapportons l’observation d’un enfant, hospitalisé dans le service de néonatologie pour des difficultés alimentaires. Les traits grossiers du visage de cet enfant et l’hypertrophie gingivale, associés à une hypotonie axiale, un encombrement des voies aériennes supérieures et une hépatomégalie modérée, ont conduit au diagnostic dès 3 semaines de vie. Le diagnostic a été confirmé par des taux urinaires anormalement élevés de dermatane- et d’héparane-sulfate et par un déficit complet de l’activité enzymatique de l’alpha-L-iduronidase lysosomale. L’enfant était homozygote pour la mutation p.W402X du gène de l’alpha-L-iduronidase (IDUA). Le tableau clinique s’est aggravé progressivement jusqu’à l’âge de 4 mois, associant dysostoses thoraco-lombaires, glaucome, dilatation ventriculaire cérébrale avec sténose cervicale du canal rachidien, cardiopathie dilatée puis hernie ombilicale. Grâce à la précocité du diagnostic, une enzymothérapie substitutive (iaronidase, Aldurazyme®, Genzyme) avait pu être instaurée dès l’âge de 5 mois et demi, permettant une stabilisation de la cardiopathie, une régression significative de la symptomatologie oto-rhino-laryngologique (ORL) et de l’hépatomégalie. La greffe de cellules souches hématopoïétiques a été réalisée à partir de sang de cordon à l’âge de 11 mois pour une préservation optimale du développement cognitif.
Hurler syndrome, the most severe form of mucopolysaccharidosis type I (MPS I), is a rare lysosomal storage disease. The overall incidence of MPS I is 0.99–1.99/100,000 live births. Accumulation of glycosaminoglycans causes the progressive dysfunction of multiple organs. We report the case of a 3-week-old newborn who was hospitalized in the Neonatal Intensive Care Unit for feeding problems. Coarse facial features and gingival hypertrophy, associated with axial hypotonia, upper airway obstruction, and moderate hepatomegaly, led to the early diagnosis of MPS I at 3 weeks of age and was confirmed by an abnormally elevated amount of dermatan and heparan sulphate in the urine and complete deficiency of alpha-L-iduronidase lysosomal enzyme activity. The child was homozygous for the p.W402X mutation, located on chromosome 4p16.3 of the alpha-L-iduronidase (IDUA) gene. The clinical condition gradually deteriorated until the age of 4 months, with thoracic and lumbar dysostoses, glaucoma, cerebral ventricular dilatation and cervical spinal stenosis, dilated cardiomyopathy, and umbilical hernia. Early diagnosis allowed enzyme replacement therapy (iaronidase, Aldurazyme®, Genzyme) started at the age of 5 months, which provided stabilization of the heart disease, significant regression of rhinologic symptoms, and regression of hepatomegaly. Cord blood hematopoietic stem cell transplantation was performed at 11 months of age, allowing optimal preservation of cognitive development.
The Heavy Photon Search experiment took its first data in a 2015 engineering run using a 1.056 GeV, 50 nA electron beam provided by CEBAF at the Thomas Jefferson National Accelerator Facility, ...searching for a prompt, electroproduced dark photon with a mass between 19 and 81 MeV/c2. A search for a resonance in the e+e− invariant mass distribution, using 1.7 days (1170 nb−1) of data, showed no evidence of dark photon decays above the large QED background, confirming earlier searches and demonstrating the full functionality of the experiment. Upper limits on the square of the coupling of the dark photon to the standard model photon are set at the level of 6×10−6. Future runs with higher luminosity will explore new territory.
The CLAS12 Micromegas Vertex Tracker Acker, A.; Attié, D.; Aune, S. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
03/2020, Volume:
957, Issue:
C
Journal Article
Peer reviewed
Open access
The Micromegas Vertex Tracker was designed to improve upon the tracking capabilities of the baseline design of the CLAS12 spectrometer in Hall B at Jefferson Laboratory. A Barrel Micromegas Tracker ...made with six concentric cylinders, each made of three 120∘-sector tiles, surrounds the Silicon Vertex Tracker, and a Forward Micromegas Tracker composed of 6 disks is placed 30 cm downstream of the liquid-hydrogen target. Both trackers sit in a 5 T solenoid magnetic field. All Micromegas elements are based on resistive technology to withstand luminosities up to 1035 cm−2 s−1, as well as on bulk technology to enforce gain uniformity and mechanical robustness. Due to the high magnetic field, dedicated electronics have been designed and displaced ∼2 m away from the detectors. The electronics readout is based on the DREAM ASICs that allow sustained operation up to 20 kHz trigger rate at the maximum luminosity.
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